At present, 5-azacytidyne and 5-aza-2-deoxycytidine are the only DNMT inhibitors that have been approved for the treatment of hematological malignancies, including acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML), and myelodysplastic disorders (MDS) [156,157]. Here, DNMT1 is linked to chronic myelomonocytic leukemia.